Over at tor.com, this fun cage match.
Okay, now, I get that the Balrog was scary. But it was basically a giant flaming monster with a whip. Set that against Smaug, a giant flaming monster with teeth and claws.
I vote for Smaug. Yep. The dragon would wipe the floor with the balrog.
It’s a fun post — check it out if you have a few minutes, and see why Austin Gilkeson, the post’s author, thinks I’m right.
With knowledge from the Silmarillion that the Balrogs were basically Maiar gone demonic, I think the Balrog would win. Especially if Smaug is a second generation dragon, not bred by Morgoth himself (which I don’t think JRRT ever covered). Even though Smaug has claws, teeth and fire. Balrogs are tough and more spirit than body.